Regulatory Matters - GPC Amendments to the Vogtle Joint Ownership Agreements (Details) - Plant Vogtle Units 3 And 4 - Georgia Power - USD ($) $ in Millions		9 Months Ended
	Jan. 11, 2018	Sep. 30, 2021	Aug. 31, 2018
Public Utilities, General Disclosures [Line Items]
Production tax credits, aggregate purchase price, maximum		$ 300
Preliminary estimated cost to complete		9,479
Additional construction capital costs	$ 3,300	$ 350
Remaining share of construction costs, agreement to pay, percentage		100.00%
Percentage of ownership interest required for voting for continuing construction			90.00%
Percentage of costs, disallowed for recovery		6.00%
Costs disallowed for recovery, period		6 months
Public utilities, extension project schedule, term		1 year
Estimated cost to complete, starting dollar amount		$ 18,380
Category I
Public Utilities, General Disclosures [Line Items]
Preliminary estimated cost to complete		8,400
Additional construction capital costs, threshold		$ 800
Category II
Public Utilities, General Disclosures [Line Items]
Percentage of construction costs, responsibility to pay		55.70%
Additional construction capital costs		$ 80
Category II | Vogtle Owners
Public Utilities, General Disclosures [Line Items]
Percentage of construction costs, responsibility to pay		44.30%
Category II | Minimum
Public Utilities, General Disclosures [Line Items]
Additional construction capital costs, threshold		$ 800
Category II | Maximum
Public Utilities, General Disclosures [Line Items]
Additional construction capital costs, threshold		$ 1,600
Category III
Public Utilities, General Disclosures [Line Items]
Percentage of construction costs, responsibility to pay		65.70%
Additional construction capital costs		$ 100
Category III | Vogtle Owners
Public Utilities, General Disclosures [Line Items]
Percentage of construction costs, responsibility to pay		34.30%
Category III | Minimum
Public Utilities, General Disclosures [Line Items]
Additional construction capital costs, threshold		$ 1,600
Category III | Maximum
Public Utilities, General Disclosures [Line Items]
Additional construction capital costs, threshold		$ 2,100